The formatting is wrong. You need to bold each section, and not just stick the image directly in the middle of them.

Speaking of which, the image is fucking huge (also not CC-Compliant), and not formatted correctly. Instead of linking directly from a website, go to the bottom of the page and click Files. Upload the image(s) you want to use. Then use the formatting on the How to Write an SCP page.

There's no such thing as a Keter/Euclid SCP. I can only think of two SCPs on the site that use multiple classes, one of which is a very, very old article, and the other one had justification in-universe and in the text to support the dual-classes. This doesn't have the justification. You have to pick one.

You have walls of text. Break up your paragraphs with more than one line-break, so your readers don't easily glaze over it.

SCP-XXXX are to be each imprisoned in a 3 meter cell made out of concrete and regularly fed D-Class Personnel everyday at 12 o' clock PM.

Does it have to be three meters? If it's any less, or any more, or if the cell isn't made out of concrete, will they break free? If we don't feed them D-Class, will they break free? If they're not fed at 12:00, will they break free? Your containment procedures have to make sense, and they need to not be a drain on resources.

SCP-XXXX are vicious humanoid creatures measuring 2 meters tall. They chase prey at a speed of up to 90 kilometers per hour within 2 minutes and can viciously take down a human within only 30 seconds of sprinting.

Bad tone. "Vicious" is not clinical. We don't know what their prey is. Nor do you even describe what these things are, or how many we have.

SCP-XXXX never shows signs of society

More bad tone. "Signs of society" is also not clinical.

D-Class are observed to immediately run away from SCP-XXXX despite reassurances of security that all SCP-XXXX will be immediately exterminated.

This makes no sense. Why? It happens all the time? Are the Foundation that dumb enough to think that they'll believe something so false?

Through a security camera, it can be observed that SCP-XXXX show signs of society, hunting, gathering and sharing in peace.

What? How do they develop technology that already exists? And out of nothing? You didn't mention this at all in the description.

My coworkers, Doctor Bright and Doctor Yenmi

I wasn't even aware this was a doctor's note until this. Furthermore, shoehorning Bright in there like that doesn't work and immensely distracts the reader.

There's so much more to get into, but you have some broad problems with tone, formatting, and over-the-topness, both in your containment and with what these things can do, that it's hard to believe. It's not scary, and it's not that impressive. I would recommend reading skips similar to the ones you want to write, and learn why they're so successful, and why they work.

I do like that you attempt to tell some kind of narrative with how these things act together, but it comes off as weird and nonsensical, considering you had described them before as "vicious" things that run fast and kill people. Shoehorning a story in there won't work, nor will shoehorning some strange anomaly that these things can do.

I already altered it to change that.
For the time of feeding, I'll change that.
It is said there that they do [REDACTED] things to victims. They do not eat them, but do something else to them as a whole when they are starving and rabid.

It's a creature (that you don't even bother describing) that just kills you in some unspecified horrible way and I guess it also spontaneously invents paleolithic technology. That's not really very interesting.

First off, that picture's already been used in an SCP, SCP-2865, and it was removed for being non-CC compliant. Either way, you can't use it for your SCP, sorry.

Your formatting (spacing) is incorrect; given that templates are available and you can refer to virtually every article on the site as an example of how the spacing should look, the lack of spaces seems sloppy.

Don't use bold for emphasis. Professional scientific documents don't do it, and it looks silly in this context.

Ditto for caps. The article is supposed to be clinical and detached, stating facts or empirical observations and not FIRE FIRE EVERYTHING IS SCARY BE SCARED RIGHT NOW.

Too much of your information is redacted. There's only so much you can expect your reader to fill in; if you have too much redaction, it looks like the author doesn't know what's going on and is expecting the reader to do the work.

What MTF was informed? There is no one MTF (there are several, each with their own specialty), so if you say an agent "contacted the MTF", people are going to be confused.

This is fundamentally still a generic monster, with a bunch of random stuff slapped onto it. What the heck is "blue fire"? How did they develop a "primitive" radio system? How does their population grow at all? Budding? Why should the reader care about any of this?

To quote vezaz, "Get away from "type of object" or "sort of creature" and instead start thinking about stories you want to tell. Start looking for moments in your everyday life that give you pause, that are unusual, or that make you go off into a daydream. Then think about bringing the reader to that same moment."

What's the story behind these things? How did they become what they are now? Were they ever special to someone? Was someone ever special to them? Are they aware of their strange state, compared to humans? What do they want? How will they get that? There's a lot more exploration you can do here—just telling the reader "they look like this" and "they do this" isn't enough in this case.

Okay, so, I think you need to… add some test history. What are some interviews with the little girl? What about sending D-class into there, to see what happened? And if it expands at a constant rate, would the box need to be expanded at the same rate?